Tapered-impedance distributed switching power amplifier

ABSTRACT

A distributed power amplifier may include a plurality of switching power amplifier sub-circuits, and a plurality of connection network sub-circuits, each of the plurality connection network sub-circuits having a characteristic impedance, wherein each of the plurality of connection network sub-circuits combines two or more of the plurality of switching power amplifier sub-circuits into a parallel or series configuration, wherein the plurality of switching power amplifier sub-circuits, the plurality of connection network sub-circuits and the characteristic impedance of each of the plurality of connection network sub-circuits are configured to present each of the plurality of switching power amplifier sub-circuits with a substantially equivalent load impedance.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related to and claims the benefit of theearliest available effective filing date(s) from the following listedapplication(s) (the “Related Applications”) (e.g., claims earliestavailable priority dates for other than provisional patent applicationsor claims benefits under 35 USC §119(e) for provisional patentapplications, for any and all parent, grandparent, great-grandparent,etc. applications of the Related Application(s)).

RELATED APPLICATIONS

For purposes of the USPTO extra-statutory requirements, the presentapplication constitutes a regular (non-provisional) patent applicationof United States Provisional Patent Application entitledTAPERED-IMPEDANCE DISTRIBUTED SWITCHING POWER AMPLIFIERS, naming DavidCripe, Scott Patten, Don Landt, and Forest Dixon as inventors, filedApr. 14, 2011, application Ser. No. 13/086,843.

TECHNICAL FIELD

The present invention generally relates to switching power amplifiercircuits, and more particularly to a tapered-impedance distributedswitching power amplifier circuits.

BACKGROUND

In the design and construction of systems for high power radio frequency(RF) generation, it is desirable to develop systems with improvedconversion efficiencies, as the operating temperatures of the componentpower amplifier (PA) transistors are often a limiting factor. A varietyof circuits have been developed in order to increase the efficiency ofan RF power amplifier by exploiting the switching characteristics of apower amplifier device. Such systems are known in the art as switchingpower amplifiers. The most common switching power amplifiers include theclass-D, class-E, and class-F switching circuits.

As shown in FIG. 1, a class-D power amplifier includes a first switchingdevice Q and a second switching device /Q arranged in a “totem pole”configuration. Each device is driven to conduct complementarily through180 degrees out of each RF cycle. The output of a class-D poweramplifier is a square-wave voltage waveform, with the amplifier beingfed from a low-impedance voltage bus. The load network of the class-Dpower amplifier includes a series-tuned band pass filter, permitting theconduction of a current waveform consisting primarily of a carrierfrequency having highly attenuated harmonics. As a result, the currentconducted by each PA switch is a half-sinusoid waveform.

Those skilled in the art will recognize that traditional power switchingdevices suffer from parasitic reactances. The parasitic reactances existdue to capacitance associated with the drain-source of a component PAtransistor and the inductance associated with the transistorinterconnections. Parasitic reactances may cause undesired resonanceswithin the PA transistor waveforms, and may degrade efficiency at higherfrequencies.

FIG. 2 illustrates a schematic view for a class-F power amplifierutilized to ameliorate the effects of the parasitic reactances of thetransistors. The class-F amplifier consists of a choke-fed,grounded-source switching device, which is connected via a quarter-wavetransmission line (labeled ¼ wave in FIG. 2) to a parallel LRC band-passfilter. The band-pass filter of the class-F PA presents a low-magnitudeimpedance to all harmonics except the fundamental of the frequency ofoperation. The ¼ wave transmission transforms the impedance in a mannerwhich presents the drain of the transistor with a high impedance to allodd-order harmonics. Consequently, the drain voltage waveform is asquare wave, while the drain current waveform is a half-sinusoid,conducted during the time frame in which the drain-source voltage is atits minimum. Moreover, the transistor interconnection inductance may beconsidered absorbed into the transmission line section.

FIG. 3 illustrates a schematic view of a push-pull class-F amplifier,which is a variation of the class-F power amplifier depicted in FIG. 2.The push-pull class-F power amplifier may be constructed by replacingthe RF choke of the tradition class-F power amplifier with an additionalswitch and transmission line. The second transistor of the push-pullclass-F power amplifier is driven in opposition to the lower device,creating a push-pull circuit.

FIG. 4 illustrates a class-E power amplifier. The class-E poweramplifier topology is capable of absorbing both the transistor parasiticshunt capacitance and the interconnect inductance into its resonantcircuit. The output network of the class-E power amplifier has a netimpedance at the frequency of operation with a nominally 52 degreeinductive component, while presenting a much larger impedance at allhigher harmonics. The switch of the class-E power amplifier is driven ata nominal 50% duty, with the drain-source voltage waveform being adamped sinusoid, which returns to zero volts prior to the commencementof the conducitve half-cycle of the switch. Moreover, the drain currentof the class-E power amplifier is a sinusoidal segment, beginning atzero amps at the commencement of the conductive half-cycle.

FIG. 5 illustrates a simplified version of the class-E power amplifiercircuit. In the simplified class-E power amplifier circuit, the outputloading circuit is placed between the supply voltage and the resonantswitch circuit.

The combination of power amplifiers, such as class-D, class-E, andclass-F power amplifiers, poses several difficulties. Power amplifiers,unlike passive components, cannot simply be connected in parallel orseries to sum their outputs. It is therefore desirable to create acircuit or system of circuits which effectively combine various poweramplifiers. More specifically, it is desirable to create a distributedamplifier utilizing a number of switching power amplifier circuits.

SUMMARY

A distributed power amplifier is disclosed. In one aspect, thedistributed power amplifier may include, but is not limited to, aplurality of switching power amplifier sub-circuits, and a plurality ofconnection network sub-circuits, each of the plurality connectionnetwork sub-circuits having a characteristic impedance, wherein each ofthe plurality of connection network sub-circuits combines at least twoof the plurality of switching power amplifier sub-circuits into asubstantially parallel configuration such that each of the plurality ofswitching power amplifier sub-circuits is presented with a substantiallyequivalent voltage waveforms, wherein the plurality of switching poweramplifier sub-circuits, the plurality of connection network sub-circuitsand the characteristic impedance of each of the plurality of connectionnetwork sub-circuits are configured to present each of the plurality ofswitching power amplifier sub-circuits with a substantially equivalentload impedance such that each of the plurality of switching poweramplifier sub-circuits has a substantially equivalent drain currentwaveform.

In another aspect, the distributed power amplifier may include, but isnot limited to, a plurality of switching power amplifier sub-circuits,and a plurality of connection network sub-circuits, each of theplurality connection network sub-circuits having a characteristicimpedance, wherein each of the plurality of connection networksub-circuits combines at least two of the plurality of switching poweramplifier sub-circuits into a substantially series configuration suchthat each of the plurality of switching power amplifier sub-circuits ispresented with a substantially equivalent current waveform, wherein theplurality of switching power amplifier sub-circuits, the plurality ofconnection network sub-circuits and the characteristic impedance of eachof the plurality of connection network sub-circuits are configured topresent each of the plurality of switching power amplifier sub-circuitswith a substantially equivalent load impedance such that each of theplurality of switching power amplifier sub-circuits has a substantiallyequivalent drain voltage waveform.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not necessarily restrictive of the invention as claimed. Theaccompanying drawings, which are incorporated in and constitute a partof the specification, illustrate embodiments of the invention andtogether with the general description, serve to explain the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the disclosure may be better understood bythose skilled in the art by reference to the accompanying figures inwhich:

FIG. 1 is a circuit diagram illustrating a Class D power amplifier.

FIG. 2 is a circuit diagram illustrating a Class F power amplifier.

FIG. 3 is a circuit diagram illustrating a push-pull Class F poweramplifier.

FIG. 4 is a circuit diagram illustrating a Class E power amplifier.

FIG. 5 is a circuit diagram illustrating a simplified Class E poweramplifier.

FIG. 6A is a circuit diagram illustrating a quarter-wave transmissionline.

FIG. 6B is a circuit diagram illustrating a T-network.

FIG. 6C is a circuit diagram illustrating a Pi-network.

FIG. 7 is a circuit diagram illustrating a distributed Class D poweramplifier, in accordance with one embodiment of the present invention.

FIG. 8 is a circuit diagram illustrating a distributed parallel modeClass F power amplifier, in accordance with one embodiment of thepresent invention.

FIG. 9 is a circuit diagram illustrating a distributed parallel modeClass E power amplifier, in accordance with one embodiment of thepresent invention.

FIG. 10 is a circuit diagram illustrating a distributed series modeClass F power amplifier, in accordance with one embodiment of thepresent invention.

FIG. 11 is a circuit diagram illustrating a distributed series modeClass E power amplifier, in accordance with one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not necessarily restrictive of the invention as claimed. Theaccompanying drawings, which are incorporated in and constitute a partof the specification, illustrate embodiments of the invention andtogether with the general description, serve to explain the principlesof the invention. Reference will now be made in detail to the subjectmatter disclosed, which is illustrated in the accompanying drawings.

Referring generally to FIGS. 6A through 11, a distributed switchingpower amplifier is described in accordance with the present disclosure.Combining multiple switching power amplifier sub-circuits using properlyconfigured intermittent connection network sub-circuits may provide amore efficient and superior distributed switching power amplifier. Thepresent invention is directed at providing a distributed switching poweramplifier consisting of a sequence of switching power amplifier (PA)sub-circuits (e.g., Class-D, Class-E, or Class-F) combined viainterposed connection network sub-circuits (e.g., quarter wavetransmission line, T network, or Pi Network), wherein the individualconnection network sub-circuits have a selected characteristic impedancein order to ensure each individual switching PA sub-circuit is presentedwith an equivalent load impedance. For instance, the successiveconnection network sub-circuits may be configured to have taperedimpedances such that each successive connection network sub-circuit hasan impedance which is incrementally increased or decreased, depending onthe chosen topology. The result being a sequence of connection networksub-circuits having a step-wise increase or decrease in impedance alongone direction of the transmission line of the distributed switching PA,as illustrated in FIGS. 7 through 11. Presenting each individualswitching PA sub-circuit with the same loading impedance aids inproviding equivalent voltage and current waveforms for each switching PAsub-circuit, a desirable characteristic of a distributed amplifiersystem. Moreover, whether the connection network sub-circuits used tocombine the sequence of switching PA sub-circuits transforms a currentwaveform or voltage waveforms will depend on the specific topology ofthe distributed switching PA. The distributed switching PA (e.g., 700,800, 900, 1000, and 1100) created by combining multiple switching PAsub-circuits may include two overarching topologies, namely a parallelconfiguration and a series configuration. Several embodiments of thedistributed switching PA are described further herein. Thesedescriptions should not be interpreted as limitations but merelyillustrations of the present invention.

Referring now to FIGS. 6A through 6C, the connection networksub-circuits utilized to interconnect the various power amplifiersub-circuits of the distributed amplifier are illustrated. FIG. 6Aillustrates a quarter-wave transmission line suitable for use as aninterconnection sub-circuit of the present invention. In one aspect, thetransmission line possesses a characteristic length, expressed in afractional wavelength at a particular frequency. In addition, thetransmission line possesses a characteristic impedance, given by thesquare root of the ratio of the value of infinitesimal inductance tocapacitance, per unit length. A quarter-wave transmission line mayperform an impedance transformation. For instance, when terminated withan impedance X, the input impedance of the transmission line having acharacteristic impedance Z is given by:

$\begin{matrix}{Z_{in} = \frac{Z^{2}}{X}} & \left( {{Eqn}.\mspace{14mu} 1} \right)\end{matrix}$

FIG. 6B illustrates a T-network interconnection sub-circuit. A T-networkmay be described by the angular phase shift for a particular RFfrequency. For a ±90 degree T-network, the characteristic impedance ofthe network will equal the magnitude of the impedances of the inductorsand capacitors of the network at the particular RF frequency.

FIG. 6C illustrates a Pi-network interconnection sub-circuit. Similar tothe T-network, a Pi-network may be described by the angular phase shiftfor a particular RF frequency. For a ±90 degree Pi-network, thecharacteristic impedance of the network will equal the magnitude of theimpedances of the inductors and capacitors of the network at theparticular RF frequency.

The interconnection sub-circuits illustrated in FIGS. 6A through 6C maybe utilized to interconnect various power amplifier sub-circuits inorder to construct a distributed power amplifier device. Reference willbe made throughout the following disclosure to transmission line,T-network, and Pi-network interconnection sub-circuits and thereimplementation in a distributed amplifier context. The above descriptionshould not be considered a limitation, but merely an illustration of theprinciples of the various interconnection sub-circuits.

Referring now to FIG. 7, a circuit diagram for a distributed switchingpower amplifier 700 constructed by combining multiple Class-D switchingpower amplifier (PA) sub-circuits 702 a-702 d is displayed. In oneembodiment, each of the Class-D switching power amplifier sub-circuits702 a-702 d may include a pair of high power switching devices (e.g.,Q1-Q8) arranged in a half-bridge configuration. For example, sub-circuit702 a may include the high powered switching devices Q1 and Q2, where Q1and Q2 are arranged in a traditional Class D half-bridge configuration.Similarly, sub-circuit 702 b, sub-circuit 702 c, and sub-circuit 702 dmay include half-bridged switching device pairs Q3-Q4, Q5-Q6, and Q7-Q7respectively. Further, the high power switching devices Q1-Q8 mayinclude, but are not limited to MOSFET switching devices.

As discussed above, the Class D switching PA sub-circuits 702 a-702 d ofthe Class D distributed switching PA 700 may provide a high efficiencypower amplification building block suitable for use at high frequencies(i.e., 100 kHz to 1 GHz). The Class D switching PA sub-circuits operateby switching output devices between and “on” and “off” state. In thecase of a MOSFET based Class D switching PA sub-circuit, in the “on”state a given amount of current flows through the Class D sub-circuit,while approximately zero voltage is present from the drain to source. Asa result, power dissipation (i.e., P=VI) is approximately zero. In the“off” state, an open circuit is present and, therefore, no current flowsthrough the device. Thus, similar to the “on” state, power dissipationin the “off” state for a Class D switching PA sub-circuit is also zero.

It is recognized that, due to the quasi-parallel arrangement of theClass D distributed switching PA, each of the switching PA sub-circuits702 a-702 d will have approximately an equivalent voltage waveform atthe switching node of the Class D half-bridge sub-circuit. It is anobject of the present invention to configure the Class D distributedswitching PA using connection network sub-circuits 704 a-704 c such thatan equivalent current waveform also exists at each of the switching PAsub-circuits 702 a-702 d. The combination of the parallel design and theintroduction of the connection network sub-circuits results in eachswitching PA sub-circuit 702 a-702 d having equivalent current andvoltage waveforms.

In one aspect of the present invention, the Class D switching PAsub-circuits 702 a-702 d may be combined using the connection networksub-circuits 704 a-704 c such that each switching PA sub-circuit 702a-702 d is presented with the same load impedance. In order to provideequal loading on each Class D switching PA sub-circuit 700 in adistributed Class D switching PA having a load impedance of Z₀ and poweramplifier sub-circuits 702 a-702 d, the connection network sub-circuits704 a-704 c between the power amplifier sub-circuits 702 a-702 d mustperform an impedance transformation.

In a further aspect, illustrated in FIG. 7, each switching PAsub-circuit 702 a-702 d must be presented with a load impedance,provided by the connection network sub-circuits 704 a-704 c, whichincreases successively with each switching PA sub-circuit progressingtoward the load. For purposes of illustration, it is assumed herein thatthe output loading of the distributed switching PA 700 is equal to thequantity “Rload,” as illustrated in FIG. 7. In one embodiment, it isrecognized that if the output loading equals Rload then switching PAsub-circuit 702 a is presented with an impedance of 4·Rload. The nextswitching PA sub-circuit 702 b may have an impedance of (4/2)·Rload.However, when the current from the first switching PA sub-circuit 702 ais summed, the effective impedance at the second switching PAsub-circuit 702 b is 4·Rload. Similarly, the impedance at the thirdswitching PA sub-circuit 702 c is (4/3)·Rload. Again, when summed withthe currents of the previous PA sub-circuits, the effective impedance atthe third switching PA sub-circuit is 4·Rload. It is recognized that theuse of this tapered impedance configuration allows for the presentationof an equivalent effective load impedance of Rload at each switching PAsub-circuit 702 a-702 d of the distributed switching PA 700.

Moreover, the impedances of the configuration described above areprovided via the connection network sub-circuits 704 a-704 c, whereinthe characteristic impedances of the connection network sub-circuits 704a-704 c are equal to the above impedances. More specifically, thecharacteristic impedances of each of the connection network sub-circuits704 a-704 c used to connect successive switching PA sub-circuits 702a-702 d for the above example are given by 4·Rload, (4/2)·Rload, and(4/3)·Rload respectively, as illustrated by Z1, Z2, and Z3 in FIG. 7.

In a general sense, the impedance for each successive node in the ClassD switching PA may be expressed by:

$\begin{matrix}{Z_{m} = {Z_{0}\left( \frac{n}{m - 1} \right)}} & \left( {{Eqn}.\mspace{14mu} 1} \right)\end{matrix}$

where Z₀ represents the load impedance of the distributed switching PA,n represents the number of switching PA sub-circuits in the distributedswitching PA, and m represents the given node. It should be noted thatwhen used in this context n must be greater than 2 and m must be equalto or greater than 2 but less than n.

It is further recognized that the connection network sub-circuits 704a-704 c may be selected to impart a 90° phase shift at the frequency ofoperation. As a result, the drive signal to each successive switching PAsub-circuit is also delayed by 90°.

In the Class D switching PA configuration, it is necessary for theoutput network to present an impedance at the harmonic frequencies thatis significantly larger than the impedance presented at the fundamentalfrequency. As a result, the preferred connection network sub-circuit foruse in the Class D switching PA configuration includes the low passT-network, illustrated in FIGS. 6B and 7, as it provides the aboverequirements.

It should be recognized that by utilizing the tapered impedances of theT-networks in order to combine Class D switching PA sub-circuits in thedistributed switching PA the current in each of the T-networks mayincrease. While the current in each connection network builds, isolationbetween adjacent switching PA sub-circuits may be provided in such a waythat the current that is drawn from each PA sub-circuit into theT-networks is controlled.

Referring now to FIG. 8, a circuit diagram for a distributed switchingpower amplifier 800 constructed by combining multiple Class-F switchingpower amplifier (PA) sub-circuits 802 a-802 d in a quasi-parallelconfiguration is displayed. As observed in the case of the Class Ddistributed switching PA, the voltage waveforms at each Class Fswitching PA sub-circuit are substantially equivalent due to theparallel nature of the parallel mode Class F distributed switching PA.In a manner analogous to the distributed Class D switching PA 700, ClassF switching PA sub-circuits 802 a-802 d may be combined utilizingconnection network sub-circuits 804 a-804 c in order to ensure the draincurrent of each Class F switching PA sub-circuit is substantiallyequivalent.

Moreover, the tapered impedance requirements present in the distributedClass D switching PA 700 also exists in the parallel mode Class Fswitching PA 800. More specifically, the impedance profile forconnection network sub-circuits 804 a-804 c must be tapered. Thetapering may occur such that, given an output load of Rload, theimpedances of the 804 a, 804 b, and 804 c connection networks requiredto ensure the current waveforms at each Class F switching PA sub-circuit802 a-802 d are equivalent are 4·Rload, (4/2)·Rload, and (4/3)·Rloadrespectively, as illustrated by Z1, Z2, and Z3 in FIG. 8. In a generalsense, not limited to the specific illustration provided above, theimpedance of each successive connection networks 804 a, 804 b, and 804 cmay be expressed using equation 1 above, in a manner similar to theClass D switching PA context.

In contrast to the Class D distributed PA 700, the preferred connectionnetwork sub-circuit for use in the parallel mode Class F switching PA800 configuration includes the Pi-network, illustrated in FIG. 6C andFIG. 8. The Pi-network selected for implementation in the parallel modeClass F context is terminated both at the input and output of thePi-network by a capacitor (e.g., C1 and C2 in FIG. 8). The capacitorterminated Pi-networks 804 a-804 c presents a low impedance to currentsat the harmonics of the fundamental frequency, as required by the ClassF switching PA sub-circuits 802 a-802 d. Further, the transmission linesT1-T4 of the Class F switching PA sub-circuits provide high impedancesto current at harmonic frequencies, which is required in order topreserve the half-sinusoidal drain current waveform of the switchingdevices Q1-Q4 of the Class F switching PA sub-circuits 802 a-802 d.

It is further recognized that each transistor Q1-Q4 of the Class Fswitching PA sub-circuits, as you pass from left to right on FIG. 8, mayhave its drive signal delayed by 90° in order to coincide with the 90°phase shift of each connection network 804 a-804 d between the switchingPA sub-circuits 802 a-802 d.

Implementation of the incrementally smaller characteristic impedancesZ1-Z3 of the Pi-network connection networks 804 a-804 c used to connectthe PA sub-circuits 802 a-802 d of the distributed PA 800 serves toequalize the drain currents in each PA sub-circuit as each PAsub-circuit contributes its individual power to the circuit 800.

It is further contemplated that the concepts described above withrespect to the described distributed parallel mode Class F switching PAmay be extended to a distributed parallel mode switching PA whichincorporates push-pull Class F switching power amplifiers similar to thepush-pull Class F amplifier illustrated in FIG. 3. For instance,multiple push-pull Class F switching power amplifiers sub-circuits maybe combined using connection network sub-circuits to form a distributedparallel mode push-pull Class F switching PA.

Referring now to FIG. 9, a circuit diagram for a distributed switchingpower amplifier 900 constructed by combining multiple Class-E switchingpower amplifier (PA) sub-circuits 902 a-902 d in a quasi-parallelconfiguration is displayed. As observed in the case of the Class D andparallel mode Class F distributed switching power amplifiers, thevoltage waveforms at each Class E switching PA sub-circuit 902 a-902 dare substantially equivalent due to the parallel nature of the parallelmode Class E distributed switching PA 900. In a manner analogous to thedistributed Class D power amplifier 700 and the distributed Class Epower amplifier 800, Class E switching PA sub-circuits 902 a-902 d maybe combined utilizing connection network sub-circuits 904 a-904 c inorder to ensure the drain current of each Class E switching PAsub-circuit is substantially equivalent.

Further, the tapered impedance requirements present in the distributedClass D switching PA 700 and the parallel mode Class F switching PA 800also exists in the parallel mode Class E switching PA 900. Morespecifically, the impedance profile for connection network sub-circuits904 a-904 c must be tapered. The tapering may occur such that, given anoutput load of Rload, the impedances of the 904 a, 904 b, and 904 cconnection networks required to ensure the current waveforms at eachClass E switching PA sub-circuit 902 a-902 d are equivalent are 4·Rload,(4/2)·Rload, and (4/3)·Rload respectively, as illustrated by Z1, Z2, andZ3 in FIG. 9. In a general sense, not limited to the specificillustration provided above, the impedance of each successive connectionnetworks 904 a, 904 b, and 904 c may be expressed using equation 1above, in a manner similar to the distributed Class D switching PA andparallel mode distributed Class F switching PA context. Additionally,

In contrast to the distributed Class D PA 700 and the parallel modedistributed class F PA 800, the series-drain choke (e.g., L1, L2, andL3) of each connection network sub-circuit 904 a-904 c may maintain theimpedance for the RF harmonics as required by the Class E sub-circuits902 a-902 d. As a result, the specific topology of the connectionnetwork sub-circuits 904 a-904 c is not critical. Consequently, a usermay implement transmission lines, a Pi-networks, or T-networks,illustrated in FIGS. 6A through 6C, as the connection networksub-circuits 904 a-904 c of the parallel mode distributed Class E PA asis convenient. For example, as illustrated in FIG. 9, transmission linesections T1-T3 may be utilized as the connection network sub-circuit 904a-904 c.

It is recognized that in each of the examples described above, theparallel-combination of PA transistors results in the output loadingbeing a fraction of the impedance seen by each individual PAsub-circuit. This is the preferred application for PA devices operatingfrom high voltage, such as GaN devices, SiC devices or vacuum tubes.

Referring now to FIG. 10, a circuit diagram for a distributed switchingpower amplifier 1000 constructed by combining multiple Class-F switchingpower amplifier (PA) sub-circuits 1002 a-1002 d in a quasi-seriesconfiguration is displayed. In contrast to the parallel modearrangements of the Class D, E and F distributed power amplifiersdescribed above, the current waveforms at each switching PA sub-circuit1002 a-1002 d are equivalent due to the series nature of the series modedistributed Class F switching PA. As a result, the connection networksub-circuits 1004 a-1004 c are utilized in order to transform thevoltage waveforms such that the voltage waveforms are substantiallyequivalent at each Class F switching PA sub-circuit 1002 a-1002 d.

In a further aspect, illustrated in FIG. 10, each switching PAsub-circuit 1002 a-1002 d must be presented with a load impedance,provided by the connection network sub-circuits 1004 a-1004 c, whichdecreases successively with each switching PA sub-circuit progressingtoward the load. For purposes of illustration, it is assumed herein thatthe output loading of the distributed switching PA 1000 is equal to thequantity “Rload,” as illustrated in FIG. 10. In one embodiment, it isrecognized that if the output loading equals Rload and there exist fourswitching PA sub-circuits (e.g., 1002 a-1002 d) then switching PAsub-circuit 1002 a is presented with an impedance of (1/4)·Rload. Thenext switching PA sub-circuit 1002 b may be presented with an impedanceof (2/4)·Rload. However, when the current from the first switching PAsub-circuit 1002 a is summed, the effective impedance at the secondswitching PA sub-circuit 1002 b is 4·Rload. Similarly, the impedance atthe third switching PA sub-circuit 1002 c is (3/4)·Rload. Again, whensummed with the currents of the previous PA sub-circuits, the effectiveimpedance at the third switching PA sub-circuit is 4·Rload. It isrecognized that the use of this tapered impedance configuration allowsfor the presentation of an equivalent effective load impedance of Rloadat each switching PA sub-circuit 1002 a-1002 d of the distributedswitching PA 1000.

Moreover, the impedances of the configuration described above areprovided via the connection network sub-circuits 1004 a-1004 c, whereinthe characteristic impedances of the connection network sub-circuits1004 a-1004 c are equal to the above impedances. More specifically, theimpedances of each of the connection network sub-circuits 1004 a-1004 cused to connect successive switching PA sub-circuits 1002 a-1002 d forthe above example are given by (1/4)·Rload, (2/4)·Rload, and (3/4)·Rloadrespectively, as illustrated by Z1, Z2, and Z3 in FIG. 10.

In a general sense, the impedance for each successive node in the seriesmode distributed Class F switching PA may be expressed by:

$\begin{matrix}{Z_{m} = {Z_{0}\left( \frac{m - 1}{n} \right)}} & \left( {{Eqn}.\mspace{14mu} 2} \right)\end{matrix}$

where Z₀ represents the load impedance of the distributed switching PA,n represents the number of switching PA sub-circuits in the distributedswitching PA, and m represents the given node. It should be noted thatwhen used in this context n must be greater than 2 and m must be equalto or greater than 2 but less than n.

Similar to the parallel mode configuration, it is further recognizedthat since the connection network sub-circuits 1004 a-1004 c may beselected to impart a 90° phase shift at the frequency of operation, thedrive signal to each successive switching PA sub-circuit is also delayedby 90°. In a complimentary fashion to the parallel mode distributedClass-F PA, the connection network sub-circuits 1004 a-1004 c mayinclude a plurality of pi-networks. Each pi-network may serve to seriescombine adjacent Class-F switching PA sub-circuits.

Referring now to FIG. 11, a circuit diagram for a distributed switchingpower amplifier 1100 constructed by combining multiple Class-E switchingpower amplifier (PA) sub-circuits 1102 a-1102 d in a quasi-seriesconfiguration is displayed. Similarly to the series mode distributedClass-F PA 1000, the current waveforms at each switching PA sub-circuit1102 a-1102 d are equivalent due to the series nature of the series modedistributed Class E switching PA. Therefore, the connection networksub-circuits 1104 a-1104 c are utilized in order to transform thevoltage waveforms such that the voltage waveforms are substantiallyequivalent at each Class-E switching PA sub-circuit 1102 a-1102 d.

Analogously to the distributed Class-E PA 1000 described above, eachswitching PA sub-circuit 1102 a-1102 d must be presented with a loadimpedance, provided by the connection network sub-circuits 1104 a-1104c, which decreases successively with each switching PA sub-circuitprogressing toward the load. The tapered impedances associated to theClass-E PA 1100 are analogous to those for the Class-F PA 1000. Morespecifically, given an output loading of Rload the impedance presentedat the switching sub-circuits 1104 a, 1104 b, 1104 c, and 1104 d are(1/4)·Rload, (2/4)·Rload, and (3/4)·Rload respectively, as illustratedby Z1-Z3 in FIG. 11. It is recognized that the use of this taperedimpedance configuration allows for the presentation of an equivalenteffective load impedance of Rload at each switching PA sub-circuit 1102a-1102 d of the distributed switching PA 1100. In a general sense, notlimited to the specific illustration provided above, the impedance ofeach successive connection networks 1104 a, 1104 b, and 1104 c may beexpressed using equation 2 above.

In a complimentary fashion to the parallel mode distributed Class-E PA,the connection network sub-circuits 1104 a-1104 c may include aplurality of quarter-wave transmission lines labeled T1-T3 in FIG. 11.Each quarter-wave transmission line may serve to series combine adjacentClass-F switching PA sub-circuits.

It is further contemplated that since the series mode distributedamplifiers 1000 and 1100 are floating, it may be necessary to provide anisolated drive circuit for these devices. Consequently, these circuitsmay provide ideal applications for optically-driven OSISE and MOSISEcircuits.

In addition to the various examples of the present invention providedabove, it is further contemplated that the concepts described herein maybe extended to numerous other embodiments. In one such embodiment, twocomplimentary series mode distributed power amplifiers (e.g.,distributed Class F 1000 or distributed Class E 1100) may be coupled ina manner analogous to the upper and lower transistors in the half-bridgeof a push-pull Class F power amplifier (illustrated in FIG. 3). Thus,applying this concept to series mode Class E or series mode Class Fdistributed amplifies a distributed Class E half-bridge or a distributedClass F half-bridge may be constructed.

In another embodiment of the present invention, the concepts used todevelop the series and parallel distributed networks described hereinmay be extended to construct a two-dimensional distributed PA network.For instance, multiple individual PA transistors may be interconnectedutilizing various combinations of transmissions lines, pi-networks,T-networks, or like impedance matching networks to form atwo-dimensional array of power amplifiers which are combined to a singlepoint within any position in the array. In a further embodiment, thisconcept may be extended to construct a three-dimensional distributed PAnetwork. For instance, multiple individual PA transistors may beinterconnected utilizing various combinations of transmissions lines,pi-networks, T-networks, or like impedance matching networks to form athree-dimensional array of power amplifiers which are combined to asingle point within any position in the array.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely exemplary, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected”, or“operably coupled”, to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable”, to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based upon the teachings herein, changes and modificationsmay be made without departing from the subject matter described hereinand its broader aspects and, therefore, the appended claims are toencompass within their scope all such changes and modifications as arewithin the true spirit and scope of the subject matter described herein.

Furthermore, it is to be understood that the invention is defined by theappended claims. It will be understood by those within the art that, ingeneral, terms used herein, and especially in the appended claims (e.g.,bodies of the appended claims) are generally intended as “open” terms(e.g., the term “including” should be interpreted as “including but notlimited to,” the term “having” should be interpreted as “having atleast,” the term “includes” should be interpreted as “includes but isnot limited to,” etc.). It will be further understood by those withinthe art that if a specific number of an introduced claim recitation isintended, such an intent will be explicitly recited in the claim, and inthe absence of such recitation no such intent is present. For example,as an aid to understanding, the following appended claims may containusage of the introductory phrases “at least one” and “one or more” tointroduce claim recitations. However, the use of such phrases should notbe construed to imply that the introduction of a claim recitation by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

Although particular embodiments of this invention have been illustrated,it is apparent that various modifications and embodiments of theinvention may be made by those skilled in the art without departing fromthe scope and spirit of the foregoing disclosure. Accordingly, the scopeof the invention should be limited only by the claims appended hereto.

It is believed that the present disclosure and many of its attendantadvantages will be understood by the foregoing description, and it willbe apparent that various changes may be made in the form, constructionand arrangement of the components without departing from the disclosedsubject matter or without sacrificing all of its material advantages.The form described is merely explanatory, and it is the intention of thefollowing claims to encompass and include such changes.

What is claimed:
 1. A distributed power amplifier, comprising: aplurality of switching power amplifier sub-circuits; and a plurality ofconnection network sub-circuits, each of the plurality connectionnetwork sub-circuits having a characteristic impedance, wherein each ofthe plurality of connection network sub-circuits combines at least twoof the plurality of switching power amplifier sub-circuits into asubstantially series configuration such that each of the plurality ofswitching power amplifier sub-circuits is presented with a substantiallyequivalent current waveform, wherein the plurality of switching poweramplifier sub-circuits, the plurality of connection network sub-circuitsand the characteristic impedance of each of the plurality of connectionnetwork sub-circuits are configured to present each of the plurality ofswitching power amplifier sub-circuits with a substantially equivalentload impedance such that each of the plurality of switching poweramplifier sub-circuits has a substantially equivalent drain voltagewaveform.
 2. The distributed power amplifier of claim 1, wherein thecharacteristic impedances of successive connection network sub-circuitsof the plurality of connection network sub-circuits are tapered.
 3. Thedistributed power amplifier of claim 1, wherein the characteristicimpedances of successive connection network sub-circuits of theplurality of connection network sub-circuits are tapered, wherein thecharacteristic impedances of successive connection network sub-circuitsof the plurality of connection network sub-circuits decreases with eachconnection network sub-circuit toward a load.
 4. The distributed poweramplifier of claim 1, wherein the plurality of switching power amplifiersub-circuits comprises at least one of a plurality of Class E switchingpower amplifier sub-circuits or a plurality of Class F switching poweramplifier sub-circuits.
 5. The distributed power amplifier of claim 1,wherein each of the plurality of connection network sub-circuitscomprise: a connection network sub-circuit configured to perform animpedance transformation.
 6. The distributed power amplifier of claim 5,wherein the connection network sub-circuit configured to perform animpedance transformation comprises at least one of a quarter-wavetransmission line sub-circuit, a pi-network sub-circuit, or a T-networksub-circuit.
 7. The distributed power amplifier of claim 5, wherein theconnection network sub-circuit configured to perform an impedancetransformation comprises: a connection network sub-circuit configured toprovide low impedance to harmonic frequency currents at a drain circuitof a switching power amplifier sub-circuit.
 8. The distributed poweramplifier of claim 5, wherein the connection network sub-circuitconfigured to perform an impedance transformation comprises: aconnection network sub-circuit configured to provide high impedance toharmonic frequency currents at a drain circuit of a switching poweramplifier sub-circuit.
 9. The distributed power amplifier of claim 1,wherein some of switching power amplifier sub-circuits of the pluralityof switching power amplifier sub-circuits include one or more MOSFETtransistors.